Craftsmen in Southeast Asia had mastered the art of bronze casting by the early centuries a.d., when ritual objects such as urns and bells were fashioned from a copper-tin alloy. In Cambodia the fine craftsmanship of the earliest surviving bronze figures, from the seventh and eighth centuries, indicates long-standing knowledge of lost-wax casting. The
techniques practiced by Khmer sculptors are unknown, but the process
generally involves making a model out of clay or plaster and encasing it in
a fireproof mold, with a layer of wax between the mold and the model. When
baked, the wax runs out and molten bronze is poured into the space left by
the melted wax.

The Vishnu reclining in cosmic sleep was cast in sections that
were then fitted together. Decorative elements, such as the armband, helped
mask the joins. The small, rectilinear patches on, for example, the
figure's forehead, chest, and upper arm indicate that casting on this
monumental scale posed problems for the sculptor. The missing insets for
the mustache, eyes, and eyebrows were probably made of precious metals such
as gold or silver. Holes in the head indicate that the god once wore a
detachable diadem.